In a battery, charge is transferred between the electrodes and the electrolyte via chemical reactions. This flow of electrons generates an electrical current that flows through an externally connected circuit. Batteries are known for their high energy density. This is why they’re used in applications that call for current draw over long periods of time. A supercapacitor’s charge-transfer process is fundamentally different. Similar to a capacitor, charge is stored electrostatically between two electrodes. A supercapacitor is different from a typical capacitor due its double-layer of stored electrical charge. In this double-layer, charges are stored electrostatically between the electrodes and a wall of oppositely charged non-specifically absorbed ions. Supercapacitors can deliver power almost immediately -- a quality that is highly desirable in backup power applications where response time in the event of a power outage is critical. Supercapacitors also have inherently better thermal management. Batteries have multiple mechanisms for internal heat generation Including their internal chemical reaction. In some cases, a sudden rise in heat can lead to thermal runaway and a possible explosion. For these reasons and more, supercapacitors have a higher cycle life, better high and low temperature performance, and better efficiency than batteries.
